Clean-operating baseboard heater

ABSTRACT

A baseboard heater is provided with diffuser means having a series of apertures for causing heated air to the exit therefrom in a series of discrete upwardly flowing columns spaced from the wall against which the heater is mounted to reduce the tendency for the heated air to deposit entrained foreign matter on the wall. Preferred dimensional relations are disclosed for the apertures in the diffuser means to ensure satisfactory performance of the heater.

United States Patent Shriver CLEAN-OPERATING BASEBOARD HEATER [75 Inventor: Charles S. Shriver, Oreland Pa. [73] Assignee: Orbit Manufacturing Company, Perkasie, Pa.

[22] Filed: March 1, 1971 211 App]. No.: 119,563

52 us. 0...; ..l65/55 [5 l Int. Cl ..F24h 9/04 [58] Field of Search ..l65/55, 57, 67, 68, 128,129

[56] References Cited UNITED STATES PATENTS 3,310,652 3/1967 7 Williams, Jr ..l65/55 Feb. 6, 1973 Primary ExaminerCharles S. Sukalo Att0rney-H0ws0n & Howson [57] ABSTRACT A baseboard heater is provided with diffuser means having a series of apertures for causing heated air to the exit therefrom in a series of discrete upwardly flowing columns spaced from the wall against which the heater is mounted to reduce the tendency for the heated air to deposit entrained foreign matter on the wall; Preferred dimensional relations are disclosed for the apertures in the diffuser means to ensure satisfactory performance of the heater.

11 Claims, 7 Drawing Figures PATENTEBFEB' ems 3.714.982

m gmum mml 6 5 FIG] (pmoR ART) CHARLES S. SHRIVER ATTYS,

CLEAN-OPERATING BASEBOARD HEATER The present invention relates to baseboard heaters; and more particularly, the present invention relates to an electric baseboard heater having a diffuser structure which operates to alter the flow pattern of the heated air exiting from the heater to reduce the tendency for airborne foreign matter to become deposited on the wall above the heater.

It is known that a baseboard heater tends to cause airborne foreign matter such as dust to become deposited on the wall above the heater during the course of operation. After a few heating seasons, the deposited dust may accumulate to such an extent as to become readily visible to the naked eye. Thus, at periodic intervals the wall above the heater must be washed or repainted.

In order to enable the consumer to select an electric baseboard heater which operates for reasonably long intervals without depositing an undesirable amount of foreign matter on the wall, the National Association of Electrical Manufacturers has established a so-called Cleanliness Test for rating the operational cleanliness of baseboard heaters. In order to obtain an acceptable rating on such test, heaters must not deposit more than a predetermined quantity of foreign matter on the wall in a prescribed time period. In the test, a small amount of iso-octane is burned in an enclosure in which the subject heater is mounted to create a large quantity of fine, black, carbon particles. The heater is energized for the prescribed time period and light reflectivity measurements are made on a sheet of white paper mounted on the surface of the wall above the heater. The reflectivity of the wall to impinging light is indicative of the operational cleanliness of the heater, with high reflectivity measurements indicating clean operation and low reflectivity measurements indicating less clean operation.

Heaters having structures capable of obtaining acceptable ratings on the aforementioned Cleanliness Test have been proposed by some manufacturers. For example, heaters having top shelves which extend three or more inches away from the wall deflect heated air away from the wall and thereby obtain acceptable cleanliness ratings. However, such shelf structures have not been entirely satisfactory since they project too great a distance into the room. As a result, useful floor space in the room is diminished; and in some instances, it has been noted that children tend to sit or stand on the shelf and cause it to bend downwardly.

There is a correlation between the air flow patterns produced by a baseboard heater in so-called shadow graph apparatus and the operational cleanliness of the heater. In shadowgraph apparatus, a beam of light is projected lengthwise of the heater through the heated air exiting therefrom to produce a shadow of the flow pattern on a light-reflective grid disposed normal to the heater at the end thereof remote from the light source. In the present invention, it has been discovered that when the shadowgraph air flow pattern is disposed substantially parallel to the wall and is spaced therefrom, the heater tends to operate in a clean mannera With the foregoing in mind, it is the primary object of the present invention to provide a novel baseboard heater which is capable of operating with a relatively high degree of cleanliness.

It is another object of the present invention to provide an improved electric baseboard heater which possesses a relatively narrow top shelf and which is capable of attaining at least an acceptable rating on the NEMA Cleanliness Test.

More specifically, in the present invention, a baseboard heater having a housing witha rear wall, a front wall cooperating therewith to form an air flow passage, and heat producing means mounted in the passage, is provided with diffuser means which is mounted in the housing above the heat producing means and which has a series of apertures for causing heated air to exit from the housing in a series of upwardly flowing columns spaced apart along the length of the heater and spaced from the wall to which the housing is mounted. The diffuser means includes a horizontally elongated plate having an inverted L- shaped transverse cross-section with a deflector flange inclining upwardly and forwardly from the rear wall of the housing and an apertured flange spanning between the deflector flange and the front wall of the housing. There is provided means to mount the diffuser plate to the rear wall in a manner which reduces conductive heat transfer from the plate to the housing; and there is provided tab means on the deflector flange of the plate to mount an elongated temperature-sensing tube above the heat-producing means. In addition, downturned extensions on the ends of the deflector flange and a lip on the bottom of the apertured flange cooperate with end members and sealing means mounted along the front wall of the housing to ensure that heated air exists only through the aperatures.

These and other objects, features and advantages of the present invention should become apparent from the following description when taken in conjunction with the accompanying drawing in which:

FIG. 1 is a perspective view of a baseboard heater embodying the present invention and having portions of its front wall broken away to expose the finned-tube, heat-producing means mounted therein;

FIG. 2 is an enlarged sectional view taken along line 22 of FIG. 1;

FIG. 3 is a view taken along line 3-3 of FIG. 2 to illustrate the configuration and spacing of the apertures in the diffuser means of the present invention;

FIG. 4 is an enlarged fragmentary view taken along line 4-4 of FIG. 3 to illustrate tab means on the diffuser means for mounting temperature-sensing means in the housing;

FIG. 5 is a schematic illustration of the air flow pattern produced in shadowgraph apparatus by a baseboard heater which does not have the diffuser means of the present invention;

FIG. 6 is a schematic illustration similar to FIG. 5 but of the air flow pattern produced by a baseboard heater having the diffuser means of the present invention; and

FIG. 7 is a schematic illustration of the dust pattern produced by the baseboard heater of FIG. 5 in the course of operation.

Referring now to the drawing, there is illustrated in FIG. 1 a baseboard heater embodying the present invention. The heater has a metal housing 11 with an upstanding rear wall 12 which mounts against the lower margin of a partition or wall in an area to be heated. A front wall 13 is removably mounted in the housing by means of spring clips 18,18 engaging in a continuous upturned lip 13a extending along its lower edge. A relatively narrow top shelf 14 extends forwardly from the rear wall 12 and is provided by reversely forming into a triangular cross-section the upper margin of the rear wall 12 (See FIG. 2). The rear and front walls 12 and 13, respectively cooperate with the top shelf 14 to form an air flow passage 15 through the housing 11. Heat producing means, in the present instance electrically energized finned tubing 16, is mounted in the air flow passage 15 and operates to cause ambient air to enter the housing 11 through an elongated inlet 15a along the front of the housing and to exit from the housing 11 through an outlet 15b along the top of the front wall 13. Although electrically energized finned tubing is preferred, the present invention may be employedsatisfactorily in baseboard heaters having finned tubing through which hot water is flowed.

A heater having the aforedescribed construction and including a conventional inclined deflector in the air flow passage produces an air flow pattern in a shadowgraph substantially as shown in FIG. 5. As illustrated therein, the air impinges on the wall at approximately 3 in. above the heater, the grid lines being 1 in. apart. As a result, foreign particles such as dust tend to become deposited on the surface of the wall above the heater in a pattern substantiallyas shown in FIG. 7 when subjected to the aforementioned NEMA Cleanliness Test. It is to be noted that dust pattern of FIG. 7 is relatively dark in an arcuate zone above the heater, indicating that the heater of FIG. 5 would not tend to operate as clean as desired.

According to the present invention, the operational cleanliness of a baseboard heater is markedly improved by causing heated air to exit from the front of the housing in a series of columns spaced forwardly of the partition to which the housing is mounted. To this end, diffuser means having a series of apertures 22,22 (FIG. 1) is mounted above the finned tubing 16 and in the air flow passage .15 in the housing 11. The diffuser means 20 is substantially coextensive in length with the finned tubing 16; and in the present instance, the apertures 22,22 are located at substantially equally spaced intervals therein. As may be seen in FIG. 2, the diffuser means 20 includes a plate 21 having an inverted L- shaped transverse cross-section with an imperforate deflector flange 21a inclining forwardly and upwardly from the rear wall 12 and a flange 21b (in which the apertures 22,22 are formed) depending from and spanning toward the front wall 13 from the forwardmost extremity of the deflector flange 21a. Preferably, the deflector flange 21 a is inclined at an angle of substantially 75 with respect to the rear wall 12; and the apertured flange 21b forms an included angle of substantially 105 with respect to the deflector flange 21a.

In the illustrated embodiment, the deflector flange 21a between the diffuser plate 21 and the front wall 13 of the housing 11. As may be seen in FIG. 2, the sealing means 23 includes an elongated strip of heat-resistant resilient material mounted on a continuous upturned lip 24 extending along the lower front edge of the apertured flange 21b. The sealing strip 23 is engaged by a continuous rearwardly downturned lip 13b extending along the uppermost edge of the front wall 13. Thus, the spring clips 18,18 operate to bias the front wall 13 downwardly to compress the sealing strip 23 and thereby effecting an air-tight joint between the diffuser plate 21 and the front wall 13. In order to prevent the escape of heated air past the ends of the diffuser plate 21, the deflector flange 21a has integral downturned extensions 25 (FIG. 1) on each end which engage over members disposed transversely to the finned-tubing 16 and extending forwardly from the rear wall 12 as for example the left-hand member 26.

For the purpose of securing the diffuser plate 21 in the housing 11, there is provided mounting means which, in the present instance, includes a downturned 1 extension 21d on the deflector flange 21a disposed along the rear wall 12. Insulating means, in the present instance a layer of asbestos fabric 27, is interposed between the extension 21d and the rear wall 12; and positive attachment of the diffuser 21 to the rear wall 12 is effected by fasteners 28,28 which extend through the extension 21d, the asbestos fabric 26, and the rear wall 12.

As an additional advantage, the diffuser plate 21 of the present invention provides tab means 30 (FIG. 4) for supporting a length of a temperature-sensing tube or probe 31 above and along a major portionof the finned-tubing 16. The probe 31 operates in conjunction with a limit switch mounted behind a panel 33 (FIG. 1) at the lefthand end of the housing to interrupt current flow to the finned tubing 16 in the event of a malfunction of the heater. As may be seen in FIGS. 2 and 4, the tab means 30 comprises a series of narrow strips 30a, 30a which are integral with the deflector flange 21a of the plate 21 and which are turned reversely upon the underside thereof to support the probe 31.

Certain dimensional relations are preferred for the apertures in the diffuser plate 21 if satisfactory operation of the heater is to be obtained. For instance, in a baseboard heater constructed substantially in accordance with FIGS. 1, 2 and 3 and having finned tubing with a nominal heating capacity of 250 watts/foot, each aperture 22,22 should have a lengthwise dimension I (FIG. 3) of 1.7 in. and a widthwise dimension w of 1.375 in. The apertures are spaced apart a dimension d between centers which in the present instance is 3.7 in. or substantially 4 in.; the area of each aperture is 2.34 in. or substantially 2 vi in. and the spacing d between the widthwise edges 22a, 22a of adjacent apertures is 2.0 in. In a heater constructed as above but having finned tubing with a lower nominal heating capacity of watts/foot the preferred lengthwise dimension l of each aperture is l.87 in. and the preferred widthwise dimension w is 1.00 in. The dimension d of the spacing of the apertures is 3.87 in. or substantially 4 in.; the area of each aperture is 1.87 in. or substantially 2 in.; and the dimension d, between the widthwise edges 22a, 22a of adjacent apertures is 2.0 in. Preferably, the upper lengthwise edges 22b, 22b of the apertures in each of the aforementioned heaters are spaced from the rear wall 12 of the housing a distance corresponding substantially to the distance between the widthwise edges 22a, 22a of the apertures.

Certain variations in the configuration, size and spacing of the apertures from the aforementioned preferred dimensional relations are permissable without adversely affecting the performance of the diffuser plate in the heater. There are limits, however beyond which satisfactory operation cannot be obtained. In determining the limits, cleanliness tests were conducted on a baseboard heater having finned tubing with a nominal capacity of 300 watts/foot and a diffuser plate with only a deflector flange forming a widthwise dimension w of approximately I A in. between the front edge of the deflector flange and the top edge of the front wall 13. The total lengthwise dimension of the deflector flange was 40 in. A series of baffles 2 inches wide were hooked over the front edge of the deflector plate; and they spanned therefrom to engage the inside edge of the downturned lip extending along the top edge of the front wall. The spacing between the baffles was varied; and cleanliness tests were conducted at the various spacings.

As a result of these tests, it was determined that the widthwise edges 22a, 22a of adjacent apertures in the diffuser plate 21 must not be spaced from one another closer than one-half of the lengthwise dimension 1 of the apertures 22,22; and they must not be spaced from one another further than twice the lengthwise dimension 1 of the apertures 22,22. In addition, the lengthwise dimension 1 of each aperture 22 must not be less than one-third nor greater than two-thirds of the center to center dimension d of the apertures 22,22; and, the lengthwise dimension 1 must be selected so as to provide a total area open to air flow of between one-third and two-thirds of the total area of the apertured flange 22b. Moreover, the ratio of length l to width w of each aperture must be between H1 and 4/1 for rectangular apertures. The widthwise dimension w in the test heaters was not varied; however, it is expected that some minor variations from this dimension would not materially affect the performance of the heater. Although rectangular apertures are illustrated in the preferred embodiment, apertures having non-rectangular configurations may be employed, for example circular or oval, in which event the aforementioned length/width ratios may be modified to provide the desired air flow areas in relation to the spacing between the apertures.

A baseboard heater constructed according to the aforementioned preferred dimensional relations produces a flow pattern in a shadowgraph substantially as illustrated in FIG. 6. As may be seen therein, the bulk of the air flow is spaced more than 3 inches from the wall against which the heater is mounted; and because the heated air exits through apertures in the front of the housing, the air flows upwardly in discrete columns for about 3 inches before blending with ambient air.

Thus, baseboard heaters having the diffuser structure of the present invention are capable of operating during cleanliness tests in such a manner as to avoid depositing dust on the wall in sufficient quantities as to be readily visible to the naked eye.

In view of the foregoing, it should be apparent that diffuser means has now been provided for use in a baseboard heater to reduce the tendency for airborne foreign matter to become deposited on the wall above the heater during its course of operation.

While preferred embodiments of the present invention have been described in detail, various modifications, alterations and changes may be made without departing from the spirit and scope of the present inven tion as described in the appended claims.

I claim:

1. In a baseboard heater having a housing with heatproducing means mounted therein, said housing having an upstanding rear wall for mounting against a partition in an area to be heated and a front wall spaced from said rear wall to form an air flow passage across said heat-producing means in said housing, the improvement comprising: a diffuser plate mounted in said flow passage above said heat-producing means, said diffuser plate having a deflector flange extending forwardly from the rear wall of said housing and a flange depending from said deflector flange and spanning toward said front wall with a series of apertures therein spaced predetermined distances from one another and from said rear wall, each aperture in said series having a lengthwise dimension measured in a horizontal direction ranging substantially between one-third and two-thirds of the center to center spacing of said apertures with the ratio of length to width of each aperture being in a range of substantially 1/1 to 4/1, whereby air heated by the heat-producing means exits from said housing in a series of discrete columns to reduce the tendency for foreign matter carried by the heated air to become deposited on the wall above the heater.

2. Apparatus according to claim 1 wherein said front wall has a rearwardly downturned lip extending along its uppermost edge and said diffuser plate has an inverted substantially L-shaped transverse cross-section with a forwardly upturned lip extending along the lower margin of its apertured flange and projecting into the space defined by said front wall lip, sealing means carried on said upturned lip to engage against said front wall and prevent heated air from flowing upwardly through said space, and including an end member disposed adjacent each end of said heatproducing means and transverse to said plate for cooperating therewith to define a heated-air plenum above the heatproducing means so that heated air exists only through the apertures in the diffuser plate.

3. Apparatus according to claim 1 wherein said housing has a top shelf extending forwardly from said rear wall and terminating rearwardly adjacent said apertures, said top shelf being spaced upwardly from said deflector flange so that said deflector flange prevents heated air from impinging on the underside of said shelf.

4. Apparatus according to claim 1 wherein said heater has elongated temperature-sensing means disposed above said heat-producing means and extending along at least a portion of its length and including responding substantially to said dimension and a lengthwise dimension preselected to provide said apertured flange with a total area open to air flow in a range of substantially one-third to substantially two-thirds of its total area per unit length of said heat-producing means, the spacing between edges of adjacent apertures in said series being in a range of substantially onehalf to substantially twice the lengthwise dimension of the adjacent apertures.

7. Apparatus according to claim 1 wherein each apertures has an upper lengthwise edge extending on the line ofjuncture of the plate-flanges and wherein the distance between widthwise edges of said apertures corresponds substantially to the spacing between said upper edge of the apertures and said rear wall of the housing.

8. Apparatus according to claim 7 wherein said heatproducing means has a capacity in a range of substantially 150 to substantially 375 watts per lineal foot and said apertures are spaced apart on substantially 4 inch centers with each aperture having an area in a range of substantially 2 in. to 2.5 in.

9. Apparatus according to claim 7 wherein the capacity of said heat-producing means is substantially 300 watts per lineal foot and each of said apertures has an area of substantially 2 in.

10. Apparatus according to claim 7 wherein the capacity of said heat-producing means is substantially 150 watts per lineal foot and each said apertures has an area of substantially 2 k in.

11. Apparatus according to claim 1 wherein said deflector flange inclines at an angle of substantially with respect to said rear wall and said apertured flange depends from said deflector flange at an angle of substantially 

1. In a baseboard heater having a housing with heat-producing means mounted therein, said housing having an upstanding rear wall for mounting against a partition in an area to be heated and a front wall spaced from said rear wall to form an air flow passage across said heat-producing means in said housing, the improvement comprising: a diffuser plate mounted in said flow passage above said heat-producing means, said diffuser plate having a deflector flange extending forwardly from the rear wall of said housing and a flange depending from said deflector flange and spanning toward said front wall with a series of apertures therein spaced predetermined distances from one another and from said rear wall, each aperture in said series having a lengthwise dimension measured in a horizontal direction ranging substantially between one-third and two-thirds of the center to center spacing of said apertures with the ratio of length to width of each aperture being in a range of substantially 1/1 to 4/1, whereby air heated by the heat-producing means exits from said housing in a series of discrete columns to reduce the tendency for foreign matter carried by the heated air to become deposited on the wall above the heater.
 1. In a baseboard heater having a housing with heat-producing means mounted therein, said housing having an upstanding rear wall for mounting against a partition in an area to be heated and a front wall spaced from said rear wall to form an air flow passage across said heat-producing means in said housing, the improvement comprising: a diffuser plate mounted in said flow passage above said heat-producing means, said diffuser plate having a deflector flange extending forwardly from the rear wall of said housing and a flange depending from said deflector flange and spanning toward said front wall with a series of apertures therein spaced predetermined distances from one another and from said rear wall, each aperture in said series having a lengthwise dimension measured in a horizontal direction ranging substantially between one-third and two-thirds of the center to center spacing of said apertures with the ratio of length to width of each aperture being in a range of substantially 1/1 to 4/1, whereby air heated by the heat-producing means exits from said housing in a series of discrete columns to reduce the tendency for foreign matter carried by the heated air to become deposited on the wall above the heater.
 2. Apparatus according to clAim 1 wherein said front wall has a rearwardly downturned lip extending along its uppermost edge and said diffuser plate has an inverted substantially L-shaped transverse cross-section with a forwardly upturned lip extending along the lower margin of its apertured flange and projecting into the space defined by said front wall lip, sealing means carried on said upturned lip to engage against said front wall and prevent heated air from flowing upwardly through said space, and including an end member disposed adjacent each end of said heat-producing means and transverse to said plate for cooperating therewith to define a heated-air plenum above the heat-producing means so that heated air exists only through the apertures in the diffuser plate.
 3. Apparatus according to claim 1 wherein said housing has a top shelf extending forwardly from said rear wall and terminating rearwardly adjacent said apertures, said top shelf being spaced upwardly from said deflector flange so that said deflector flange prevents heated air from impinging on the underside of said shelf.
 4. Apparatus according to claim 1 wherein said heater has elongated temperature-sensing means disposed above said heat-producing means and extending along at least a portion of its length and including tab means integral with said deflector flange and located at spaced intervals for engaging and supporting said temperature sensing means.
 5. Apparatus according to claim 1 including means mounting said diffuser plate to the rear wall of said housing, said mounting means including an integral downturned extension on said deflector flange disposed along the rear wall of said housing, insulating means disposed between the rear wall of said housing and said extension, and means extending at spaced intervals through said extension, said insulating means, and housing rear wall for fastening said extension and hence said diffuser plate to the housing.
 6. Apparatus according to claim 1 wherein said apertured flange has a predetermined widthwise dimension between said deflector flange and said front wall and each of said apertures has a widthwise dimension corresponding substantially to said dimension and a lengthwise dimension preselected to provide said apertured flange with a total area open to air flow in a range of substantially one-third to substantially two-thirds of its total area per unit length of said heat-producing means, the spacing between edges of adjacent apertures in said series being in a range of substantially one-half to substantially twice the lengthwise dimension of the adjacent apertures.
 7. Apparatus according to claim 1 wherein each apertures has an upper lengthwise edge extending on the line of juncture of the plate-flanges and wherein the distance between widthwise edges of said apertures corresponds substantially to the spacing between said upper edge of the apertures and said rear wall of the housing.
 8. Apparatus according to claim 7 wherein said heat-producing means has a capacity in a range of substantially 150 to substantially 375 watts per lineal foot and said apertures are spaced apart on substantially 4 inch centers with each aperture having an area in a range of substantially 2 in.2 to 2.5 in.2
 9. Apparatus according to claim 7 wherein the capacity of said heat-producing means is substantially 300 watts per lineal foot and each of said apertures has an area of substantially 2 in.2
 10. Apparatus according to claim 7 wherein the capacity of said heat-producing means is substantially 150 watts per lineal foot and each said apertures has an area of substantially 2 1/2 in2. 